The human monocytic cell line THP-1 cell was first derived from the peripheral blood of a 1 year old male with acute monocytic leukaemia. It is now a widely used cell line with properties similar to the properties of "human monocyte-derived macrophages". It easily differentiates or matures into macrophage (phagocytes) and adheres to cell culture flasks when stimulated with phorbol esters (PMA) or vitamin D3. Therefore this cell line is widely used in the study of foam cell formation in atherosclerotic processes. Furthermore, stimulated THP-1 cells are an appropriate substitute to blood monocyte models as it easily divides and can be maintained in cell culture for long periods. A major characteristic of THP-1 cells are that they express Fc and C3b receptors and lack both surface and cytoplasmic immunoglobulins.

The first THP-1 cell line was cultured from a 1 year old boy with monocytic leukemia isolated by Tsuchiya et al. (1980). The major findings were that the cell line expresses Fc and C3b receptors and lack cytoplasmic immunoglobulins. THP-1 cells were characterised by action of alpha-naphthyl butyrate esterase that was inhibited by Sodium fluoride, action of lysozyme (enzyme responsible for breaking down the polysaccharide walls), return of T lymphocyte response to lectin protein Con A.

Tsuchiya S, Yamabe M et al. 1980. Establishment and characterization of a human acute monocytic leukemia cell line (THP-1). Int J Cancer. 26(2): 171-6

Maintaining THP-1 cells

RPMI 1640 + 2mM Glutamine + 0.05mM 2-Mercaptoethanol (reducing agent not essential) + 10% Fetal Calf Serum (FCS). Penicillin (100 units/ml) and streptomycin (100 μg/ml) are further added to prevent bacterial contamination. Maintain cultures between 1000 to a million cells/ml at 5% CO2 in 37 degree centigrade.

Freezing THP-1 cells

When cells are growing at an early passage at the log phase of growth, it can be harvested and frozen as follows. Cells are centrifuged at 1000g and then suspended in FCS + 10% Glycerol as a cryoprotectant. Freeze in -80 degrees wrapped in bubble wrap for 24 hours and then in immerse in liquid nitrogen.

Precautions

Although no there no confirmation of virus or toxicity from this cell line, it is required that work is carried out in a Level 2 containment safety cabinet. Workers on human tissues are required to have a hepatitis B vaccine for protection against infection with blood-borne viruses.

Similar properties withhuman monocyte derived macrophages

Produce cytokine IL-1

Produce CO2 on phagocytosis

Differentiate into macrophages in DMSO and PMA (phorbol 12-myristate 13-acetate) and adhere to surface of flask and show different morphology

Difficult cell line for transfection